1. Field of the Invention
The present invention relates to a vehicle air conditioning apparatus which includes a heating heat exchanger and electrical heating members integrated with the heating heat exchanger. More particularly, the present invention relates to a control unit for electrically controlling the electrical heating members.
2. Description of Related Art
In a conventional air conditioning apparatus for a vehicle described in DE 19752676, electrical heating members composed of a PCT heater are disposed in an air passage on a downstream air side of a heating heat exchanger and in a foot air outlet from which air is blown toward the foot area of a passenger in a passenger compartment. When temperature of hot water flowing into a heating heat exchanger is low, the electrical heating members are turned on, so that air blown into the passenger compartment is quickly heated by heat generated from the electrical heating members. However, in the conventional air conditioning apparatus, the electrical heating members are disposed at different positions to be separated from the heating heat exchanger. Therefore, an assembling operation of the electrical heating members into the air passage is necessary to be performed separately from an assembling operation of the heating heat exchanger into the air passage. Further, the electrical heating member disposed in the foot air outlet is only used during a foot mode in which the foot air outlet is opened. Therefore, the electrical heating member disposed in the foot air outlet cannot be used for improving defrosting performance of a windshield during a defroster mode, and it is necessary to switch the electrical operation of the electrical heating members in accordance with a selected air outlet mode.
Further, JP-A-5-69732 proposes a hot water type heating heat exchanger integrated with plural electrical heating members. In the heating heat exchanger, when temperature of hot water (engine-cooling water) flowing into the heating heat exchanger is lower than a set temperature, electrical power is supplied to the electrical heating members to heat air using heat generated from the electrical heating members. However, because electrical power supplied to the electrical heating members is not controlled in accordance with a vehicle state such as a battery charging level, heating capacity for the passenger compartment cannot be controlled finely according to the vehicle state, and immediate-heating performance for the passenger compartment may be deteriorated.